1. Field of the Invention
This invention relates to the field of computer graphics systems. More particularly, this invention relates to generation of high resolution virtual reality images.
2. Art Background
Computer graphics traditionally deals with the generation of an image on a screen in a manner visually faithful to the representation of an image by a camera. However, the human visual system evolved not for viewing photographs, but for close range binocular (stereo) viewing of 3D objects, with unrestricted head motion. Holograms and holographic stereograms support this, providing proper perspective and motion parallax effects. Unfortunately, technology does not yet allow these forms of display to be created in real-time.
An alternate technique for emulating close range examination of a physical object by a user employs a head-tracking device. If a 3D stereo image display system is augmented by a head-tracking device, the synthetic viewpoint of the rendering process can be made to correspond to the actual dynamic physical viewpoint of the user. Such a system dynamically computes a stereo pair of images that has the same appearance as a hologram, and the virtual object appears to remain stationary when the viewer tilts his head, or moves his head to look around its side or over its top. For further discussion regarding head tracked systems, refer to Paley, W. B. Head-tracking Stereo Display, Techniques and Applications, Proceedings of SPIE, February 1992.
In practice, making a head-tracked stereo display system work involves achieving an accurate mapping of the mathematical viewing pyramid onto the real world of physical CRT's, biological heads, and human eyeballs. In case of the head mounted displays that are used in today's virtual reality systems, the mathematical-to-physical mapping may only be generally approximated.
However, .many applications of virtual reality do require highly accurate mapping of physical and virtual objects. For example, for a surgeon viewing 3D computer aided tomography (CAT) scan data overlaid on a patient during surgery, the positions of the virtual and real objects must coincide within a fraction of an inch. Also, in electronics and mechanical repair it is desirable to overlay diagnostic and schematic information directly on physical components having dimensions on the order of fractions of an inch. Moreover, with accurate physical/virtual correspondence, direct interaction with virtual objects is possible using virtual tools. For further discussion of virtual reality applications, refer to Rheingold, H. Virtual Reality, Summit Books, 1991. See also, Cyberspace: first steps, edited by Benedikt, M., The MIT Press, 1992.
Past viewing projection methods used in computer graphics assume that the light-emitting image plane is, in fact, planer. However the phosphor screen of a typical CRT is by design a section of a sphere or of a cylinder, and is viewed through a thick glass faceplate that has an index of refraction significantly higher than that of air. In conventional computer graphics, the inaccuracies produced by ignoring these effects are imperceptible. But for high resolution stereo, the errors produced are significant enough to require correction.
As will be described, the present high resolution virtual reality system enables accurate head-tracked stereo display, and provides the corrections necessary to achieve accurate visual correspondence of physical objects and virtual objects.